Advanced Windows PowerShell Scripting Video Training

Advanced Windows PowerShell Scripting Video Training
Advanced Windows PowerShell Scripting Video Training

Thursday, September 22, 2016

ByValue for Specific Objects

This is post 5 of 7 in this series.
Many cmdlets accept pipeline input ByValue, but only for very specific objects.  After all, do you think it would be wise to do this?

PS C:\> Get-Process | New-Mailbox

Probably not. We are going to see if this command will work.

PS C:\> Get-Service -Name "Bits" | Stop-Service

First off, let’s get the objects TypeName that is produce by the left hand side of the command.

PS C:\> Get-Service -Name "Bits" | GM


   TypeName: System.ServiceProcess.ServiceController

Name                      MemberType    Definition                                        
----                      ----------    ----------                                        
Name                      AliasProperty Name = ServiceName                                
RequiredServices          AliasProperty RequiredServices = ServicesDependedOn              
Disposed                  Event         System.EventHandler Disposed(System.Object, Syst..

We can see that the object is of type ServiceController. Next, we need to see if any parameter of Stop-Service will accept input from the PowerShell pipeline.

PS C:\> Get-help Stop-Service -Parameter *

I shortened the list to only the parameters that meet this criteria.

-InputObject
    Specifies ServiceController objects that represent the services to stop. Enter a
    variable that contains the objects, or type a command or expression that gets the
    objects.
   
    Required?                    true
    Position?                    1
    Default value                none
    Accept pipeline input?       True (ByValue)
    Accept wildcard characters?  false
   

-Name
    Specifies the service names of the services to stop. Wildcard characters are permitted.
   
    Required?                    true
    Position?                    1
    Default value                none
    Accept pipeline input?       true(ByValue,ByPropertyName)
    Accept wildcard characters?  false

There are only two parameters where theAccept pipeline input attribute is True.  Now we need to look at the object types that each parameter will accept. Remember, we are passing a ServiceController object to this cmdlet.  The –Name parameter only accepts String objects so no go there. The –InputObject parameter does accept our ServiceController object.  That is why we are able to execute
PS C:\> Get-Service -Name "Bits" | Stop-Service





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